Seasonal Changes in the Effects of Starvation on Metabolic Rate and Regulation of Body Weight in Svalbard Ptarmigan

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Abstract
Svalbard ptarmigans deposit large amounts of body fat during the autumn. When the fat stores were at their fullest (in Sept./Oct.) resting metabolic rate was 100 kcal gk-1 day-1 after 5 day of starvation. In Dec. when voluntary food intake was at its lowest, resting metabolic rate was 88 kcal kg-1 day-1, being unaffected by 5 days of starvation. Weight loss during starvation in Sept./Oct.,Nov., Dec. and Jan. was 18.7, 16.3, 11.0 and 12.9 g days, respectively. The daily energy expenditure of starved birds at the same time of the year. The Svalbard ptarmigan does not increase its activity during episodes of starvation in winter. Starved birds responded to resumed feeding with hyperphagia until their body weight reached the body weight of ad lib fed control birds. Body weight in the Svalbard ptarmigan is regulated according to a seasonally changing set-point. The potential durability of the body fat reserves of starving Svalbard ptarmigan was assessed at monthly invervals during the dark part of the winter.